adapters. Also available for the IBM ServeRAID adapters are a range of battery backed cache options to provide even greater stability to your customer’s data.

5.2.5.6 RAID Summary

RAID should always be considered when availability and file size of business critical data is an issue. Individual requirements will dictate the final RAID solution for the customer.

In all cases there are advantages and disadvantages of each RAID solution in practical terms. These should be considered when selecting your hard disk configuration for the IBM Netfinity and J.D. Edwards’ OneWorld implementation.

Refer to Table 2 for an overview of advantages and disadvantages of RAID solutions. You should review 5.2.6, “Fault Tolerance” for further details regarding overall fault tolerance of the system.

Table 2. IBM Netfinity Hardware Considerations

Considerations

Advantages

Disadvantages

 

 

 

RAID 0

Very high read and write

Failure must be dealt with

 

performance

immediately with loss of access to

 

 

users

 

 

Data integrity - low

 

 

 

RAID 1

Data integrity - high

Degrades performance

 

 

(two writes for each data write)

 

 

Expensive, size of single disk is

 

 

limitation

 

 

 

Disk Duplexing

Data integrity - very high

Single disk is size limitation

 

Performance is greater than RAID 1

Expensive - 2x disk capacity for data

 

Higher fault tolerance than RAID 1

 

 

Second disk controller

 

 

 

 

Enhanced RAID 1

Data integrity - very high

Performance impact

 

High fault tolerance

Performance - parity/checksum

 

No reboot on single disk failure

overhead

 

 

 

RAID 5

Data integrity - very high

Performance impact

 

High fault tolerance

Performance - parity/checksum

 

No reboot on single disk failure

overhead

 

 

 

5.2.6 Fault Tolerance

As discussed in 5.2.5, “RAID Support” on page 39 there are limits to availability, and fault tolerance capabilities that various RAIDs can offer within the system by themselves. This section will look at other ways of offering fault tolerant solutions to get closer to the ultimate goal of 100% availability.

If we look at the most likely failures, given the history of IT technology, then we can start to look at the gain on reliability and availability versus cost of implementing the relevant solution. The most likely failures are discussed here in some order of "likely to fail", as this order can vary from country to country dependent upon many local factors.

Sizing, Considerations, and Recommendations

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IBM B73.3 manual Fault Tolerance, RAID Summary, Considerations Advantages Disadvantages